Electrical network system



Aug. 30, 1938. YUK-WING LEE ET AL 2,123,257

ELECTRICAL NETWORK SYSTEM Filed July 7, 1936 6 Sheets-Sheet l O UTPU7 gaINVENTODS YuK- Wnvcs LEE Noeazer VVIENEP BY V ATTORNEY Aug. 30, 1938.YUK-WING LEE El AL 2,123,257

ELECTRICAL NETWORK SYSTEM Filed July 7, 1936 r 6 Sheets-Sheet 2 PEP" 5"INVENTORS YUK'WING LEE FIG. 2. NOIPBEPT VVIENEI? ATTORNEY Aug. 30, 1938.YUK-WING LEE ET AL 2,128,257

ELECTRICAL NETWORK SYSTEM Filed July 7, 1956 6 Sheets-Sheet 3 17500&

| i 155 52 Y \AIINVEFTORS UK- we 55 El i-i BY NOPBEQT VVIENEI? ATTORNEYAug. 30, 1938. YUK-WING LEE ET AL 2,128,257

ELECTRICAL NETWORK SYSTEM Filed July 7, 1936 6 Sheets-Sheet 4 zazaahzzzsoh zzzao OUTPUT 4 INVENTORS F'IGA- YUK'VV/NG LEE NOPBEET W/ENEQ BYMW ATTORNEY Aug. 30, 1938. Yu .w LEE ET AL 2,128,257

ELECTRI CAL NETWORK SYSTEM Filed July 7, 1936 6 Sheets-Sheet 5 OUTPUT YAI/NVEFTORS UK- we 55 a NORBEQT VV/ENER BY Q ATTORNEY Aug. '30, 1938.

YUK-WING LEE ET AL ELECTRICAL NETWORK SYSTEM Filed July 7, 1936 6Sheets-Sheet 6 PHASE- A AMPL/TUDE- COPPECT/NG COQPECT/NG NETWOQK oNETWOIPK PHASE- caQQEcT/Ns AMPLIFIER AMPLITUDE?- COPDEC TING o NETWORK aFIG. 7.

' AMPLITUDE- COPIPECT/NG NETWOPK AMPLIFIEP INVENTOR S YuK WING LEEPatented Aug. 30, 1938 UNITED STATES PATENT OFFICE ELECTRICAL NETWORKSYSTEM York Application July 7, 1936, Serial No. 89,336

1'1 Claims.

This invention relates to electrical corrective network systems, andparticularly to a new type of electrical network, and to a new method ofcomputing the constants and values of the re- 5 spective elements of anetwork system.

In electrical communication systems, and in other systems wherevibrations of difierent frequencies undergo an electricaltransformation, it is desirable to have corrective networks to correctthe distortion in the electrical vibrations due to the inherentproperties of or imperfections in the parts of the systems. Thecorrective network may also serve to control electrical vibrations inaccordanc with specifications required for a special purpose which mayor may not be corrective, or may be partially corrective.

Distortion in electrical vibrations may be in amplitude or in phase orin both amplitude and phase. Amplitude distortion is the unequal changein amplitude of vibrations of different frequencies; and phasedistortion is the unequal change in phase relations of the vibrations ofdifferent frequencies. Generally, an amplitudecorrecting network servesto equalize the amplitude change, and a phase-correcting network servesto bring the vibrations into the same phase relations as those existingin the original vibrations; These conditions are necessary for the truereproduction of vibrations of different frequencies. Various networkshave been invented for such corrections, but they are not subject toadjustment or conveniently adapted to preliminary computations.

An object of this invention is to correct distortion in electricaltransmission systems and in other similar systems. I

Another object is to incorporate in a single network system adjustablemembers adapted to produce any attainable amplitude-frequencycharacteristic, the adjustment for any characteristic to be done withthe aid of simple computations, or in accordance with calibrations, orrapidly by experiment.

Still another object is to provide a network system having any desiredattainable amplitude-frequency characteristic, and whose design requiresonly simple calculations.

A still further object is to correct both amplitude and phasedistortions in electrical transmission and other similar systems by theinsertion into such systems of two different but supplementarycorrective networks having adjustable or non-adjustable members.

A further object of this invention is to provide an electrical networksystem having any desired attainable amplitudefrequency andphasefrequency characteristics.

According to this invention, a network system having an adjustableamplitude-frequency characteristic but a fixed phase-frequencycharacteristic is obtained by the construction of a network system inaccordance with a Fourier series and the provision of means by which thecircuit elements representing the coefficients of the series may bevaried in such a manner that any amplitude-frequency characteristic maybe simulated. A part of this network system is a lattice network of anumber of sections which are similar in structure, but different invalue. The lattice network is combined with a system of variable andfixed resistances through a set of transformers. The system ofresistances is connected mechanically in such a manner that each of anumber of separate mechanical connections may be assigned to controlindependently the amplitude of electrical vibrations of a particularfrequency. The amplitude-frequency characteristic of the whole system isa smooth curve passing through all the values at the particularfrequencies.

Other objects and structural details of this invention will be apparentfrom the following description when read in connection with theaccompanying figures, wherein:

Fig. 1 illustrates an electrical network system of this invention;

Fig. 2 illustrates a modified form of the electrical network system ofFig. 1;

Figs. 3 to 5 illustrate sample network systems of this invention withspecific values of the network elements;

Fig. 6 illustrates a phase-correcting network system directly incombination with a network system of this invention;

Fig. 7 illustrates a phase-correcting network system in combination witha network system of this invention through amplifier means; and

Fig. 8 illustrates a network system of this invention in combinationwith amplifier means.

It has been shown in U. S. Patent No. 2,024,900, issued December 1'7,1935, to N. Wiener and Y. W. Lee, that a network characteristic Y(0),having been expanded into a Fourier series of the form wherein do, al,(12,11: are constants,

and 0:2 tankw, k being a positive constant, and w being 21l' times thefrequency, may be physically represented by a network system such asshown in Fig. 10 of that patent.

A modification in the aforementioned network system in accordance withthe following theory renders complicated calculations unnecessary in theadjustment of the system for any amplitudefrequency characteristic.Another advantage in this change is that the characteristic of the newnetwork system responds to adjustment in a l s e s s n u u s 0 loll-Iomuch more desirable manner since in the new network system variations inthe different portions of the characteristic are practically independentof one another.

Consider the series These resistances are arranged in pairs (with theexception of the resistances at the extreme right), and are so connectedthat when viewed from the transformer, the total resistance is constantirrespective of the positions of the shafts.

which, written in another form, is

( Evidently, the modulus 11(9) of Series (2) is and its phase I (9) isEvidently, the amplitude-frequency characteristic depends upon thequantities on .afl.

which are made variable by the means described later. The phasecharacteristic, however, does not involve these quantities and thereforeremains independent of the amplitude adjustment.

In order to relate the changes in the amplitude characteristic to thequantities (to an we may begin by specifying the particular values 00 0"of the variable 0 which correspond to the particular frequencies atwhich the amplitude adjustment is to be made. This gives +211 cos :10

Further, the system of resistances is such that As explained in theaforementioned patent, when viewed from the input side of eachtransformer, the total resistance should be +2a cos n0 +2a cos n0 fromwhich, we obtain, by elementary methods in algebra assuming that alltransformers have a ratio of transformation of unity. Here L, inhenries, is

Ia.'='Al..L $6 644.} 'vi b rlsli k669i; new 4 .1. as:

wherein Ao,o, A04, Ao,2, Aim, Ao are constants. It now appears that theadjustment can be made by expressing the quantities do an as linearcombinations of the quantities which specify the desired amplitude atthe frequencies of reference.

A physical structure which secures this desired dependence of an a uponthe specified ampiitudes l/(OO) M011) is shown in Fig. 1. S0, S1, S2,S3, Sn are shafts each connecting a column of sliding contacts togetherso that each of the two inductances of the last section (the bottomsection as shown in the figure) of the lattice network; and C, infarads, is each of the two capacitances of that section, thus making tobe expressed in ohms. Similar to Equation (12) of the previous patent,the angle 0 is 0:2 tan-Writ. (10) The dotted lines and the dot-and-dashlines indicate, respectively, the positive and negative values of Ao,o,Ao,1, Ao,z, A0,: A0, of Equation (7). The output side of eachtransformer is shunted by a resistance of value and a connection is madeat the middle except at M where a sliding contact may takethe place of afixed connection. The point M determines the zero position of theshafts. The movement of this point from top to bottom corresponds to thedisplacement of the zero point from the extieme left to the extremeright of the columns of resistances. The portion of each column to theright of the zero position may be taken to represent thepositive valuesof the network characteristic, and the portion to the left, the negativevalues. Although an amplitude-frequency characteristic is alwayspositive, it is sometimes easier to produce a required characteristic ofcertain irregularities by considering portions of itasnegativ'e. Whilethe amplitude of the network characteristic may be adjusted asdescribed, the phase characteristic is unafiected by the adjustment solong as no positive coefficient is replaced by a negative one, and hasthe value given by Equation designed so that the shafts S0, S1, S2, S3,and S4 control the network characteristic at the same frequencies asthose in the previous case. The input impedance remains as 1944 ohms ofpure resistance.

A distinguishing feature of ,the network systems herein described isthat they have a fixed phase characteristic independent of thevariations in the systems of resistances. This property of the networksystems is a very useful one. In an electric network, a change in theamplitude characteristic is usually accompanied by a change in the phasecharacteristic and vice versa. These changes are related to each other,and although the relation is important in the study of network behavior,its existence is often an obstacle in engineering design problems. In agreat many electrical problems, the separate control of amplitudecharacteristic and phase characteristic is much desired.

A particular merit of this network system is that, when viewed from theinput end, as usually operated, it has the impedance characteristic of apure resistance, and that when the network is adjustable, the value ofthis resistance is unaffected by the adjustment. This greatlyfacilitates the computation of the characteristic which the network musthave to produce a desired eiTect, and minimizes the deleterious effectof reflection of oscillations at the network, which and R is added sothat .O'OIIOOQQI-olnoolcoo e e n s The. zero point of each column ofresistances is at the middle position. Other features of this networksystem are essentially the same as those described hereinbefore.

Fig. 3 shows a sample network system designed in accordance with theprinciples of this invention described above. This is an example of thegeneral network system of Fig. 1. Shafts S0, S1, S2, S3 and S4 aredesigned to control the network characteristic at frequencies of zero,188. 454, 1097, and infinite cycles per second. Although the first andlast shafts theoretically control vibrations at zero, and infinitecycles per second, they may be utilimd to adjust vibrations at anyfrequency between zero and l88cycles per second, and any frequencybetween 1097 and infinite cycles per second, respectively. The extremevalues are used here as a matter of convenience in computations.According to the theory of this invention, other values may be usedinstead. The transformers of this network are to operate betweenimpedances of 17,500 ohms. The input impedance is 1944 ohms of pureresistance.

Figs. 4 and 5 show sample networks of the general network of Fig. 2.These networks are very critical in wave filters of most previous types.

A suitable type of phase-correcting network system, for example, one ofthose diclosed and claimed in the aforementioned patent, may be combineddirectly as shown in Fig. 6, or indirectly through an amplifier as shownin Fig. 7, with a network system of this invention thereby providing anew network system capable of producing any desired amplitude-frequencyand phase-frequency characteristics. The network system of thisinvention controls the amplitudefrequency characteristic, and, having afixed phase-frequency characteristic itself, allows the phase-correctingnetwork system to control the phase-frequency characteristic.

The device of this invention thus produces a single electrical networksystem having adjustable members by means of which any desired networkcharacteristics can be produced, thereby enabling a single correctivesystem to be used for any purpose. Such a system is to be distinguishedfrom the prior art, in which a given network was adaptable only to .asingle amplitude characteristic curve, and was adapted to othercharacteristic curves only after complete rebuilding and reconstructionof the values of all the component parts.

The invention does not, however, necessarily reside in the adjustablefeatures as above-mentioned, since it is possible by the computationprocess of this invention to produce a network having non-adjustableelements, which can be computed and constructed in size according to thedesired characteristic curve of the network. When so constructed, thesystem, although nonadjustable without partially rebuilding, nevertheless p'roduces a simple, convenient network system of high efllciencywhich stimulates with a high degree of accuracy the characteristic curveobtainable from computation.

The system of the invention may be used to feed directly into a repeateror other amplifying device, as shown in Fig.8, or may be interpolatedbetween the stages of an amplifier. It may also be used to feed directlyor indirectly into a phonograph cutter orother instrument transformingelectrical vibrations into a mechanical form. Among its applications,but not exhausting them, are a use in connection with communicationcircuits for filtering, balancing, orcompensating purposes; a use, whenin combination with a phase-correcting network, in connection withtelevision circuits, to which the combination is peculiarly adapted,owing to the fact that it gives a ready control over phase distortion'as well as amplitude distortion; a use in the production of tones ornoises of predetermined distribution of energy in frequency; a use inthe recording and reproducing of sound; a use as an instrument in thecalibration of electrical and acoustical systems, for laboratory,

medical and other purposes; and a use in the determination of whatquality of response in a sound reproducing device is most desirable orpleasing to the human car. It is possible to embody the principles ofthis device in mechanical or acoustical form, in accordance with thewellknown analogies between electrical vibrating systems and mechanicalor acoustical vibrating systems.

While the above description discloses a limited number of embodiments ofthe device of this invention, it is possible to produce still otherembodiments without departing from the spirit thereof, and it isdesired, therefore, that only such limitations shall be imposed upon theappended claims as are stated therein or required by the prior art.

What is claimed is:

1. An electrical network system with adjustable amplitude-frequencycharacteristic, and with phase-frequency characteristic independent ofadjustment, said system comprising means for progressively shifting thephase of an input signal, a plurality of pairs of electrical paths forwithdrawing therefrom voltages differing in phase, means for combiningsaid voltages, and means including variable impedances for adjusting therelative amplitudes of said voltages.

2. An electrical networksystem with adjustable amplitude-frequencycharacteristic, phasefrequency characteristic independent of adjustment,and input impedance that of a constant resistance, said systemcomprising means for progressively shifting the phase of an inputsignal, a plurality of pairs of electrical paths for withdrawingtherefrom voltages difiering in phase, means for combining saidvoltages, and means 3. An electrical network system with adjustableamplitude-frequency characteristic, and.

with phase-frequency characteristic and input impedance both independentof adjustment, said system comprising means for progressively shiftingthe phase of an input signal, a plurality of pairs of electrical pathsfor withdrawing therefrom voltages differing in phase, means forcombining said voltages, and means including variable impedances foradjusting the relative amplitudes of said voltages.

4. An electrical network system comprising means for progressivelyshifting the phase of an input signal, a plurality of electrical pathsfor withdrawing therefrom voltages diflfering in phase, means forcombining said voltages, a plurality of variable impedances, and aseries of con trols for adjusting said variable impedances, whereby theoutput to input voltage ratio of the system may be controlled over aportion of the frequency spectrum without substantially influencing saidvoltage ratio at certain other specific frequencies.

5. An amplitude-correcting network having a constant, non-reactive inputimpedance, said network comprising means for progressively shifting thephase of an input signal, a plurality of electrical paths forwithdrawing therefrom voltages differing in phase, means for combiningsaid voltages, a plurality of variable impedances, and a plurality ofcontrols for adjusting said variable impedances, whereby the absolutevalue of the ratio of the input to the output voltage may beindependently adjusted at any one of a plurality of fixed frequencieswithout affecting either the phase-frequency characteristic or saidinput impedance.

6. An amplitude-correcting network comprising a plurality of tandemconnected four-terminal transducers for progressively shifting the phaseof an input signal, a plurality of electrical paths for tapping ofivoltages from said trans ducers, means for combining said voltages, anda plurality of variable resistances associated with said paths by meansof which the amplitude-frequency characteristic may be adjusted withoutafiecting the phase-frequency characteristic of said network.

7. An amplitude-correcting network having a constant, nonereactive inputimpedance and com prising means for progressively shifting the phase ofan input signal, a plurality of electrical paths for withdrawingtherefrom voltages differing in phase, means for combining saidvoltages, and

.a plurality of variable resistances for adjusting the relativeamplitudes of said voltages, whereby the amplitude-frequencycharacteristic of said network may be adjusted without afiecting itsphase-frequency characteristic.

8. An amplitude-correcting network comprising means for progressivelyshifting the phase of an input signal, means for extracting therefromphase-shifted voltages at a plurality of points, means for combiningsaid voltages, and means comprising a plurality of variable resistancesfor individually controlling the amplitudes of said voltages whereby theamplitude-frequency characteristic of said network may be adjustedwithout affecting either its phase-frequency characteristic or its inputimpedance.

9. An amplitude-correcting network having a constant, non-reactive inputimpedance and comprising means for progressively shifting the phase ofan input signal, a plurality of electrical paths for tapping oilphase-shifted voltages, means for combining said voltages, a pluralityof variable resistances in each of said paths, and a plurality ofcontrols associated with said variable resistances by mean of which theamplitude-frequency characteristic may be adjusted without affectingeither the phase-frequency characteristic or the input impedance of saidnetwork.

10. A variable amplitude-correcting network comprising means forprogressively shifting the phase of an input signal, a plurality ofelectrical paths for withdrawing phase-shifted voltages therefrom, meansfor combining-said voltages, and a plurality of controls for regulatingthe relative amplitudes of said voltages, whereby theamplitude-frequency characteristic of said network may be adjustedindependently at any one of a plurality of frequencies without affectingthe amplitude-frequency characteristic at any of the other of saidfrequencies.

11. A network comprising a plurality of connected transducer sectionsfor progressively shifting the phase of an input signal, a plurality ofelectrical paths connected to said sections at different points, meansfor tapping off voltages from said paths, and means for combining saidvoltages, the magnitudes of said voltages corresponding to thecoefllcients a0, a1, as, as, an of the expansion of theamplitude-frequency characteristic to be simulated into a series of theform an+2an 1 cos 0+2Gn-2 cos 20+2Gm-3 cos 30+ +2ao cos 110 whereini=\/- l 0:2 tan kw, It being a positive constant, and to being 2'! timesthe frequency.

13. An electrical network system comprising a plurality of tandemconnected transducers for subjecting the signal voltage to progressivephase shift, means comprising variable impedances for tapping oilvoltages at a plurality of Junction points of said transducers, meansfor combining said voltages, and a plurality of controls for adlustingsaid variable impedances whereby the amplitude frequency characteristicof said system may be independently adjusted at any one of a pluralityof frequencies without materially affecting its phase frequencycharacteristic.

14. An electrical network system comprising means for subjecting asignal voltage to progressive phase shift, a plurality of electricalpaths for tapping off phase-shifted voltages at a. plurality of points,means for combining said voltages, a plurality of pairs of variableimpedances associated with said paths, and a unitary control for saidvariable impedances whereby the magnitude of each of said impedances maybe varied without changing the total impedance of each of said pairs.

15. An electrical network system comprising a plurality of transducersfor progressively shifting the phase of an input signal, a plurality ofelectrical paths for tapping oil phase-shifted voltages from saidtransducers, means for combining said voltages, a plurality of pairs ofvariable impedances in each of said paths, and a plurality of controls,each of said controls being associated with a plurality of said pairs ofvariable impedances in a plurality of said paths, and the adjustment ofeach of said controls operating to increase the magnitude of one of theimpedances of each of said pairs with which said control is associatedwhile at the same time decreasing by a like amount the magnitude of theother variable impedance forming said pair.

16. An electrical network system comprising a plurality of transducersfor progressively shifting the phase of an input signal, a plurality ofsimilar pairs of electrical paths leading from said transducers, meansfor combining the output voltages of said paths, a plurality of pairs ofvariable impedances in each of said paths, and a plurality of controls,each of said controls being associated with a pair of said impedances ineach of said paths and operating to adjust the amplitudefrequencycharacteristic of said system over a portion of the frequency spectrumwithout substantially altering said characteristic at certain otherspecific frequencies.

17. An electrical network system comprising a plurality of transducersfor progressively shifting the phase of an electrical vibration, aplurality of electrical paths for tapping off phase-shifted vibrationsfrom said transducers, means for combining said phase-shiftedvibrations, a plurality of pairs of variable impedances in each of saidpaths, and a unitary control operative to adjust each of said variableimpedances of a pair in each of said paths, whereby theamplitude-frequency characteristic of said system may be adjustedwithout materially affecting its phase-frequency characteristic.

, YUK-WING LEE.

NORBERT WIENER.

